Fallback to flag defined value for storage dir in case docker info doesn't provide the storage dir.
Fallback to flag defined value for storage dir in case docker info
doesn't provide the storage dir.

Signed-off-by: Vishnu kannan <8c9a7175bd62235d51889a4697184181a7bcfb30@google.com>

datawisesystems/cadvisor,IFTTT/cadvisor,ainsleyc/cadvisor,derekwaynecarr/cadvisor,pwittrock/cadvisor,timstclair/cadvisor,jhjeong-kr/cadvisor,IFTTT/cadvisor,erSitzt/cadvisor,linux-on-ibm-z/cadvisor,ncdc/cadvisor,ainsleyc/cadvisor,ncdc/cadvisor,jhjeong-kr/cadvisor,erSitzt/cadvisor,timstclair/cadvisor,guoshimin/cadvisor,derekwaynecarr/cadvisor,guoshimin/cadvisor,IFTTT/cadvisor,BrickXu/cadvisor,pwittrock/cadvisor,ncdc/cadvisor,derekwaynecarr/cadvisor,ncdc/cadvisor,dchen1107/cadvisor,dchen1107/cadvisor,linux-on-ibm-z/cadvisor,erSitzt/cadvisor,shilpamayanna/cadvisor,BrickXu/cadvisor,erSitzt/cadvisor,guoshimin/cadvisor,f0/cadvisor,f0/cadvisor,ainsleyc/cadvisor,IFTTT/cadvisor,timstclair/cadvisor,dchen1107/cadvisor,IFTTT/cadvisor,ainsleyc/cadvisor,erSitzt/cadvisor,pwittrock/cadvisor,jhjeong-kr/cadvisor,BrickXu/cadvisor,datawisesystems/cadvisor,jhjeong-kr/cadvisor,linux-on-ibm-z/cadvisor,derekwaynecarr/cadvisor,f0/cadvisor,ncdc/cadvisor,derekwaynecarr/cadvisor,f0/cadvisor,shilpamayanna/cadvisor,BrickXu/cadvisor,dchen1107/cadvisor,dchen1107/cadvisor,BrickXu/cadvisor,jhjeong-kr/cadvisor,f0/cadvisor